Selectors API Level 2

Selectors, which are widely used in CSS, are patterns that match against elements in a tree structure. The Selectors API specification
defines methods for retrieving Element nodes from the DOM by matching against a group of selectors, and for testing if a given
element matches a particular selector. It is often desirable to perform DOM operations on a specific set of elements in a
document. These methods simplify the process of acquiring and testing specific elements, especially compared with the more
verbose techniques defined and used in the past.